σ-adduct

The product formed by the attachment of an electrophilic or nucleophilicentering group or of a radical to a ring carbon of an aromatic species so that a new σ-bond is formed and the original
conjugation is disrupted. (This has generally been called a 'σ-complex', but adduct is more appropriate than complex according to the definitions given.) The term may
also be used for analogous adducts to unsaturated (and conjugated) systems in general.